...
eg. "iterateOver": "json.twitter_entities.user_mentions"
Metadata field nesting is also supported using dot notation, in which case they are looped over to generate calls with _value/_iterator/_index
This is the same as iterating over a metadata array to obtain entities using Manual entities.
For more information concerning metadata fields and support for nested fields, see section Manual entities.
See detailed example below
...
Create one association for every combination of entities of specified types. Also referred to as combinatorial association.
eg. "iterateOver": "entity1/entity2/geo_index",
...
Create one association for every pair (/set) of entities of specified types. Also referred to as lock-step or additive association.
eg. "iterateOver": "entity1,entity2"
...